A Printed Circuit Board (PCB) is a copper clad laminate designed to provide point-to-point electrical connections. Reinforcements used include paper, glass and resin systems including phenolics, epoxies, polyimides, and PTFE (Polytetrafluorethylene) thermoplastic. Composite PCBs have been injection molded from PEI (Polyetherimide), PES (Polyethersulfone) and PEEK (Polyetheretherketone). The most widely used PCB substrate is the FR-4 glass/epoxy laminate.